1. Field
Disclosed herein is an article for magnetic heat exchange and a method of fabricating a working component for magnetic heat exchange.
2. Description of Related Art
Practical magnetic heat exchangers, such as that disclosed in U.S. Pat. No. 6,676,772, may include a pumped recirculation system, a heat exchange medium such as a fluid coolant, a chamber packed with particles of a working material which displays the magnetocaloric effect and a means for applying a magnetic field to the chamber. The working material can be said to be magnetocalorically active.
The magnetocaloric effect describes the adiabatic conversion of a magnetically induced entropy change to the evolution or absorption of heat. Therefore, by applying a magnetic field to a magnetocalorically active working material, an entropy change can be induced which results in the evolution or absorption of heat. This effect can be harnessed to provide refrigeration and/or heating.
Magnetic heat exchangers are, in principle, more energy efficient than gas compression/expansion cycle systems. They are also considered environmentally friendly as chemicals such as chlorofluorocarbons (CFC) which are thought to contribute to the depletion of ozone levels are not used.
In practice, a magnetic heat exchanger requires magnetocalorically active material having several different magnetic phase transition temperatures in order to provide cooling over a wider temperature range. In addition to a plurality of magnetic phase transition temperatures, a practical working medium should also have a large entropy change in order to provide efficient refrigeration and/or heating.
A variety of magnetocalorically active phases are known which have magnetic phase transition temperatures in a range suitable for providing domestic and commercial air conditioning and refrigeration. One such magnetocalorically active material, disclosed for example in U.S. Pat. No. 7,063,754, has a NaZn13-type crystal structure and may be represented by the general formula La(Fe1-x-yTyMx)13Hz, where M is at least one element of the group consisting of Si and Al, and T may be one or more of transition metal elements such as Co, Ni, Mn and Cr. The magnetic phase transition temperature of this material may be adjusted by adjusting the composition.
Consequently, magnetic heat exchanger systems are being developed in order to practically realise the potential advantages provided by these magnetocalorically active materials. However, further improvements are desirable to enable a more extensive application of magnetic heat exchange technology.